Sintered compact and light emitting device

ABSTRACT

A sintered compact includes a wavelength conversion region containing a phosphor material that performs wavelength conversion of primary light and emits secondary light, and a holding region provided to be in contact with the wavelength conversion region. The wavelength conversion region and the holding region are integrated.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2016-132803 filed onJul. 4, 2016 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND 1. Technical Field

The disclosure relates to a sintered compact and a light emittingdevice, and especially to a sintered compact and a light emittingdevice, which perform wavelength conversion of primary light from alight source and emit secondary light.

2. Description of Related Art

A light emitting device is used, in which a LED (light emitting diode)or a semiconductor laser is used as a light source and a wavelengthconversion member containing a phosphor material performs wavelengthconversion, thereby obtaining white light. In such a light emittingdevice, primary light such as blue light and ultraviolet light isemitted from the light source and irradiates the wavelength conversionmember, and the phosphor contained in the wavelength conversion memberis excited by the primary light and emits secondary light such as yellowlight. Then, colors of the primary light and the secondary light aremixed and white light is emitted outside.

In Japanese Patent Application Publication No. 2012-221633 (JP2012-221633 A), a vehicle lighting fixture is proposed, in which asemiconductor laser is used as a light source. When a semiconductorlaser is used as a light source, a characteristic appears that primarylight with a large output and a narrow width of wavelength is obtained,but directivity is very strong and the light irradiates a small region.Therefore, compared to a case where a LED is used as a light source, theprimary light with a large output irradiates an extremely small regionof a wavelength conversion member, and white light is emitted. Thus, alight emitting device having high directivity is obtained.

Meanwhile, in the wavelength conversion member of the light emittingdevice, heat is generated simultaneously with the wavelength conversionof the primary light. In particular, in the case where a semiconductorlaser is used as a light source, the primary light intensivelyirradiates a small region, temperature of the wavelength conversionmember increases easily. Since the phosphor contained in the wavelengthconversion member has a characteristic that its temperature isassociated with wavelength conversion efficiency, when a temperaturechange is too large, it is not possible to perform appropriatewavelength conversion, thereby causing a problem that sufficient whitelight is not obtained.

SUMMARY

FIG. 12A is a schematic view showing an example of a method for fixing awavelength conversion member in a light emitting device in which asemiconductor laser serves as a light source. In the light emittingdevice, in which the semiconductor laser is used as the light source, asolid wavelength conversion member 2 containing a phosphor material isarranged on a surface of a light extraction part 1 that is made fromsapphire or the like that transmits primary light, and the wavelengthconversion member 2 is fixed to the light extraction part 1 by anadhesive 3. The semiconductor laser serving as the light source isarranged at a position away from the wavelength conversion member 2, andis not shown.

FIG. 12B is a schematic view showing another example of a method forfixing a wavelength conversion member in a light emitting device inwhich a semiconductor laser serves as a light source. In this example,an opening is previously formed in a light extraction part 1 of thelight emitting device, and a wavelength conversion member 2 is insertedin the opening. An adhesive 3 is injected between a side surface of thewavelength conversion member 2 and an inner surface of the opening ofthe light extraction part 1, and the wavelength conversion member 2 isfixed to the light extraction part 1. In this example, the lightextraction part 1 does not need to be a material that transmits primarylight, and a ceramic material or the like may be used.

In the light emitting devices shown in FIG. 12A and FIG. 12B, since thewavelength conversion member 2 is fixed by the adhesive 3, heatgenerated in the wavelength conversion member 2 is transferred to thelight extraction part 1 through the adhesive 3 and dissipated. Ingeneral, the light extraction part 1 is made from sapphire or ceramics,and the adhesive 3 is made from glass, silicone resin or the like, andthese materials have relatively low thermal conductivity. Therefore, itis difficult to favorably dissipate heat generated in the wavelengthconversion member 2.

Therefore, the disclosure provides a sintered compact and a lightemitting device that are able to efficiently dissipate heat generatedwith wavelength conversion.

A sintered compact according to the first aspect of the disclosureincludes a wavelength conversion region containing a phosphor materialthat performs wavelength conversion of primary light and emits secondarylight, and a holding region provided to be in contact with thewavelength conversion region. The wavelength conversion region and theholding region are integrated.

In the above aspect, since the wavelength conversion region and theholding region are integrated, the holding region is able to hold thewavelength conversion region without using an adhesive, and heatgenerated with the wavelength conversion is dissipated efficiently.

In the foregoing aspect, the holding region may have higher thermalconductivity than that of the wavelength conversion region.

Further, in the foregoing aspect, the holding region may have astructure in which a minute second ceramic material is dispersed insidea first ceramic material, and the first ceramic material and the secondceramic material are intertwined with each other three-dimensionally.

Furthermore, in the foregoing aspect, the first ceramic material mayhave higher thermal conductivity than that of the wavelength conversionregion.

Yet further, in the foregoing aspect, a refractive index differencebetween the first ceramic material and the second ceramic material maybe 0.2 or larger.

A light emitting device according to the second aspect of the disclosureincludes the sintered compact and a light emitting element that emitsthe primary light.

According to the disclosure, it is possible to provide the sinteredcompact and the light emitting device, which are able to efficientlydissipate heat generated with wavelength conversion.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the disclosure will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG. 1 is a schematic sectional view of a light emitting device 10 in anembodiment;

FIG. 2A is a schematic sectional view of a structure of a wavelengthconversion member 14 in the first embodiment;

FIG. 2B is an enlarged schematic sectional view of structures of awavelength conversion region 14 a and a holding region 14 b;

FIG. 3A is a process view of a manufacturing method for the wavelengthconversion member 14;

FIG. 3B is a process view of the manufacturing method for the wavelengthconversion member 14;

FIG. 3C is a process view of the manufacturing method for the wavelengthconversion member 14;

FIG. 3D is a process view of the manufacturing method for the wavelengthconversion member 14;

FIG. 4 is a conceptual view of how heat is transferred in the lightemitting device 10 in the first embodiment;

FIG. 5A is a schematic sectional view of a structure of a wavelengthconversion member 14 in a modification of the first embodiment;

FIG. 5B is a schematic sectional view of a wavelength conversion region14 a that is enlarged so that details are shown;

FIG. 6 is a schematic sectional view of a lighting fixture unit 20 inthe second embodiment;

FIG. 7 is a schematic sectional view of a light emitting device 40 inthe third embodiment;

FIG. 8 is a schematic sectional view of a light emitting device 50 inthe fourth embodiment;

FIG. 9 is a schematic sectional view of a light emitting device 60 inthe fifth embodiment;

FIG. 10A is a schematic sectional view of a configuration example of awavelength conversion member 14 in the sixth embodiment;

FIG. 10B is a schematic sectional view of a configuration example of thewavelength conversion member 14 in the sixth embodiment;

FIG. 11 is a schematic sectional view of a light emitting device 70 inthe seventh embodiment;

FIG. 12A is a schematic view of an example of a method for fixing awavelength conversion member in a light emitting device according to arelated art in which a semiconductor laser serves as a light source; and

FIG. 12B is a schematic view of an example of a method for fixing awavelength conversion member in a light emitting device according to arelated art in which a semiconductor laser serves as a light source.

DETAILED DESCRIPTION OF EMBODIMENTS

The first embodiment of the disclosure is explained in detail below withreference to the drawings. The same reference numerals are used for thesame or equivalent components, members, processing shown in each of thedrawings, and duplicated explanation is omitted as appropriate. FIG. 1is a schematic sectional view of a light emitting device 10 in theembodiment.

The light emitting device 10 is provided with a stem 11, a semiconductorlaser 12, a case part 13, and a wavelength conversion member 14. In thelight emitting device 10, the semiconductor laser 12 emits primary lightL1 that irradiates the wavelength conversion member 14, and the color ofthe primary light L1 is mixed with secondary light obtained fromwavelength conversion performed by the wavelength conversion member 14,thereby allowing white light L2 to be emitted outside. FIG. 1 shows thelight emitting device 10 of, but not limited to, a so-called CAN typepackage, and various types of packages for a semiconductor laser may beused.

The stem 11 is a member on which the semiconductor laser 12 is mountedand the case part 13 is fixed, and is provided with a lead pin, a heatsink and so on (not shown) so that electric power is supplied fromoutside to the semiconductor laser 12 and heat generated in thesemiconductor laser 12 is transferred outside. Although a material forthe stem 11 is not particularly limited, metal with good heatdissipation, such as copper, is preferred.

The semiconductor laser 12 is a semiconductor element where electricpower is supplied and a laser beam is oscillated. Although a materialfor the semiconductor laser 12 is not particularly limited, anitride-based semiconductor is used when blue light or ultraviolet lightis irradiated as the primary light L1. Device structures of thesemiconductor laser 12, such as a resonator structure, an electrodestructure, and a current confinement structure, are not particularlylimited either, and structures that are appropriate for getting requiredlight emission intensity and oscillation wavelength may be used. In theembodiment, the semiconductor laser 12 is shown as an element that emitsthe primary light L1. However, the element is not limited to thesemiconductor laser as long as it is a light emitting element that emitsthe primary light L1 whose wavelength is converted by the wavelengthconversion member 14, and may be a light emitting diode, an organic EL,and so on.

The case part 13 is a member arranged so as to cover the semiconductorlaser 12 on top of the stem 11, and is provided with a cylindrical sidewall raising from the stem 11, and an upper surface. There is an openingin the center of the upper surface of the case part 13, and thewavelength conversion member 14 is fixed to the opening. Although amaterial for the case part 13 is not limited, a metallic material withexcellent thermal conductivity is preferred in order to favorablytransfer heat generated in the wavelength conversion member 14 to thestem 11.

The wavelength conversion member 14 is a sintered compact in which awavelength conversion region 14 a and a holding region 14 b are incontact with each other and formed integrally. The wavelength conversionmember 14 is fixed to the opening of the case part 13 and works as apart that extracts light from the light emitting device 10.

FIG. 2A is a schematic sectional view of a structure of the wavelengthconversion member 14 in the first embodiment, and FIG. 2B is an enlargedschematic sectional view of structures of the wavelength conversionregion 14 a and the holding region 14 b. As shown in FIG. 2A and FIG.2B, the wavelength conversion member 14 in the embodiment is providedwith the wavelength conversion region 14 a and the holding region 14 b.

The wavelength conversion region 14 a is a part containing a phosphormaterial, which is excited by the primary light L1 irradiating from thesemiconductor laser 12 and emits the secondary light. Then, the colorsof the primary light L1 and the secondary light are mixed, therebyallowing the white light L2 to be emitted outside. Here, an example isshown in which the colors of the primary light L1 and the secondarylight are mixed so that the white light L2 is emitted. However, aplurality of phosphor materials may be provided so that the secondarylight in a plurality of colors are emitted, and the white light L2 maybe emitted as a result of mixture of the colors of the secondary light.An example is shown in which the light L2 to be emitted is white light,but the light L2 may be other monochromatic light, or may have a colorother than the white color, which is obtained by mixture of a pluralityof colors.

A size of the wavelength conversion region 14 a only needs to be largerthan a region irradiated with the primary light L1 from thesemiconductor laser 12, and allow appropriate wavelength conversion ofthe primary light L1 to obtain the secondary light. For example, thewavelength conversion region 14 a has a thickness of around severalhundreds μm, and a diameter of around 0.1˜several mm. The phosphormaterial contained in the wavelength conversion region 14 a is a ceramicphosphor because it is sintered simultaneously with the holding region14 b as described later. As a specific material, ceramic phosphorobtained by sintering a ceramic body made from Y₃Al₅O₁₂, or YAG (yttriumaluminum garnet) powder is most preferred. By using a YAG sinteredcompact as the wavelength conversion region 14 a, wavelength of theprimary light L1, which is blue light, is converted, thus emitting thesecondary light, which is yellow light, and color mixture of the primarylight and the secondary light produces white light.

The holding region 14 b is a part that is formed integrally and sinteredsimultaneously with the wavelength conversion region 14 a, and holds thewavelength conversion region 14 a. A material for the holding region 14b is not particularly limited. However, in order to favorably transferheat generated in the wavelength conversion region 14 a, it is preferredthat the holding region 14 b has higher thermal conductivity than thewavelength conversion region 14 a, and that the thermal conductivity ofthe holding region 14 b is 20 W/mK or higher.

Also, as shown in FIG. 2B, the holding region 14 b has a structure inwhich a second ceramic material 15 b and a third ceramic material 15 care intertwined with each other three-dimensionally inside a firstceramic material 15 a. The thermal conductivity of the holding region 14b means thermal conductivity of the entire ceramics having the structurein which these materials are intertwined with each otherthree-dimensionally.

The first ceramic material 15 a is a phase that is in contact with thewavelength conversion region 14 a and formed continuously throughout theentire holding region 14 b, and phases of the second ceramic material 15b and the third ceramic material 15 c are intertwined with each otherthree-dimensionally inside the first ceramic material 15 a. Although amaterial for the first ceramic material 15 a is not particularlylimited, it is preferred that the first ceramic material 15 a is madefrom a material having higher thermal conductivity than those of thesecond ceramic material 15 b and the third ceramic material 15 c. Bymaking the first ceramic material 15 a using a material having higherthermal conductivity than those of the rest of the ceramic materials,heat generated in phosphor 14 c inside the wavelength conversion region14 a is easily transferred through the first ceramic material 15 a anddissipated outside as shown by black arrows in FIG. 2B.

Further, it is preferred that a material for the second ceramic material15 b or the third ceramic material 15 c has a refractive indexdifference of 0.2 or larger from the first ceramic material 15 a. Whenthe plurality of ceramic materials have large refractive indexdifferences from each other, as shown by outlined arrows in FIG. 2B,light advancing from the wavelength conversion region 14 a towards theholding region 14 b is reflected by interfaces among the first ceramicmaterial 15 a to the third ceramic material 15 c that are intertwinedwith each other three-dimensionally. This makes the holding region 14 ba white region as a whole, allowing the holding region 14 b to alsoserve as a light reflecting part that is able to prevent light leakagein a lateral direction. Also, light is caused to return towards thewavelength conversion region 14 a and extracted outside from thewavelength conversion region 14 a.

The holding region 14 b described herein is made from the three types ofmaterials, which are the first ceramic material 15 a to the thirdceramic material 15 c. However, the number of types of the materials isnot limited as long as the holding region 14 b has a structure in whicha plurality of ceramic materials are intertwined with each otherthree-dimensionally.

When an appropriate combination of materials as the first ceramicmaterial 15 a to the third ceramic material 15 c is selected and acomposition ratio and synthesizing temperature are set appropriately forsintering, the above-mentioned holding region 14 b has the structurewhere each of the materials does not become a compound and each phase isintertwined with one another three-dimensionally. Table 1 showscombinations of thermal conductivity and the refractive index ofspecific ceramic materials, as well as examples of synthesizingtemperature and composition ratios. As shown in Table 1, when Al₂O₃ isselected as the first ceramic material 15 a, YSZ (Y₂O₃ stabilized ZrO₂)and TiO₂ (rutile type) may be used as the second ceramic material 15 band the third ceramic material 15 c. Also, when MgO is selected as thefirst ceramic material 15 a, YSZ may be used as the second ceramicmaterial 15 b.

TABLE 1 Refractive index difference Synthe- The first ceramics Thesecond ceramics between sizable Compo- Heat Refrac- Heat Refrac- thefirst temp- sition conductivity tive conductivity tive and seconderature ratio No. Material [W/m · k] index Material [W/m · k] indexceramics [° C.] [mol %] 1 Al₂O₃ About 30 1.76 YSZ*¹ About 3 2.1 0.34800~1800 Al₂O₃ is 8.5~88  2 Al₂O₃ ↑ ↑ TiO2 About 8 2.7 0.96 800~1200Al₂O₃ is (Rutile) 7.5~87  3 MgO About 60 1.7 YSZ About 3 2.1 0.4800~2100 MgO is 22.4~94.6 *¹Y2O3stabilizedZrO2

Next, a manufacturing method for the wavelength conversion member 14 isexplained by using FIG. 3A˜FIG. 3D. First, as shown in FIG. 3A, a greensheet 14 a′, in which raw materials for the wavelength conversion region14 a are mixed, and a green sheet 14 b′, in which raw materials for theholding region 14 b are mixed, are prepared. Then, a layered green sheetis made, in which the green sheet 14 a′ is sandwiched between the greensheets 14 b′. For example, the green sheet 14 a′ containing YAG phosphoris used, and a composite material containing the plurality of ceramicmaterials shown in Table 1 is used as the green sheet 14 b′.

Next, as shown in FIG. 3B, the layered green sheets obtained are pressedby using a warm isostatic pressing (WIP) device, and the green sheet 14a′ and the green sheets 14 b′ are adhered to one another.

Next, as shown in FIG. 3C, the adhered layered green sheets are sinteredsimultaneously, and a sintered compact is obtained, which has a layerstructure where the wavelength conversion region 14 a is sandwichedbetween the holding regions 14 b. When YAG is used as the phosphormaterial contained in the wavelength conversion region 14 a, thecombination No. 1 or No. 3 in Table 1 is selected as the materials forthe holding region 14 b, and the sintering temperature is set to1500˜1600 C.°.

Finally, the sintered compact having the obtained layer structure isdivided by dicing, etc., thereby obtaining the wavelength conversionmember 14 that is a sintered compact in which the holding regions 14 bare in contact with both sides of the wavelength conversion region 14 aand sintered integrally.

FIG. 4 is a conceptual view of how heat is transferred in the lightemitting device 10 of the embodiment. The wavelength conversion member14 of the light emitting device 10 is irradiated by the primary light L1emitting from the semiconductor laser 12. A black arrow in FIG. 4schematically shows a path of heat from the wavelength conversion region14 a. As stated earlier, since the holding region 14 b has higherthermal conductivity than that of the wavelength conversion region 14 a,heat is transferred favorably to the case part 13 through the holdingregions 14 b that are in contact with side surfaces of the wavelengthconversion region 14 a, respectively, and sintered simultaneously, andthen heat is dissipated. Further, as described above, since a pluralityof ceramic materials having the refractive index differences of 0.2 orlarger from each other are intertwined with one anotherthree-dimensionally in the holding region 14 b, light advancing from thewavelength conversion region 14 a towards the holding region 14 b isreflected without being transmitted through the holding region 14 b, andtaken out from the wavelength conversion region 14 a as shown by arrowsL2 in the drawing.

As stated above, in this embodiment, the wavelength conversion member 14has the wavelength conversion region 14 a, which contains the phosphormaterial that performs wavelength conversion of the primary light andemits the secondary light, and the holding region 14 b, which isprovided to be in contact with the wavelength conversion region 14 a.Also, the wavelength conversion member 14 is the sintered compact inwhich the wavelength conversion region 14 a and the holding region 14 bare sintered simultaneously and integrally. Thus, the sintered compactin this embodiment is able to efficiently dissipate heat generated withwavelength conversion.

Next, a modification of the first embodiment is explained with referenceto FIG. 5A and FIG. 5B. FIG. 5A is a schematic sectional view of astructure of a wavelength conversion member 14 in the modification ofthe first embodiment, and FIG. 5B is a schematic sectional view of awavelength conversion region 14 a that is enlarged so that details areshown. In this modification, the wavelength conversion region 14 a ofthe wavelength conversion member 14 has a layer structure havingwavelength conversion layers 14 d and heat transport layers 14 e.

The wavelength conversion layer 14 d is a layer containing a phosphormaterial that is excited by primary light L1 emitted from asemiconductor laser 12, and emits secondary light. Specific materialsfor the wavelength conversion layer 14 d are similar to those stated inthe foregoing first embodiment.

The heat transport layer 14 e is a layer made from a transparentmaterial that transmits the primary light L1 and the secondary light.The transparent heat transport layer 14 e means that the heat transportlayer 14 e has high total light transmittance. Linear transmittance maybe low, and it is preferred that the total light transmittance is 80% orhigher, for example. It is also preferred that a material used for theheat transport layer 14 e has higher thermal conductivity than that ofthe wavelength conversion layer 14 d.

As shown in FIG. 5A and FIG. 5B, the wavelength conversion region 14 ahas a structure in which the wavelength conversion layer 14 d and theheat transport layer 14 e are layered alternately. Because of this, heatgenerated in the wavelength conversion layers 14 d is transferredfavorably to the holding region 14 b through the heat transport layers14 e, and heat generated with wavelength conversion is dissipatedefficiently. Further, since the heat transport layer 14 e has high totallight transmittance and is transparent, the heat transport layer 14 edoes not block the primary light L1 from the semiconductor laser 12 andthe secondary light obtained after wavelength conversion in thewavelength conversion layer 14 d, thereby achieving both emission of theprimary light L1 and extraction of the secondary light, and heatdissipation.

In FIG. 5A and FIG. 5B, an example is shown in which three wavelengthconversion layers 14 d and three heat transport layers 14 e are layeredalternately. However, the number of the layers is not limited, and thenumber may be larger or one each. Thicknesses of the wavelengthconversion layer 14 d and the heat transport layer 14 e may be similaror different, and a ratio of the thicknesses may be set as appropriatedepending on a balance between wavelength conversion in the wavelengthconversion layer 14 d and heat transportation in the heat transportlayer 14 e.

The wavelength conversion layer 14 d and the heat transport layer 14 emay be laminated to each other alternately by using an adhesive such assilicone resin, or green sheets may be bonded together and sinteredintegrally. By using the warm isostatic press and the sinteringtechnology described in the first embodiment, the holding region 14 b,the wavelength conversion layer 14 d, and the heat transport layer 14 eare sintered simultaneously. Then, reflection at an interface betweenthe layers is reduced, and efficiency in extraction of the primary lightL1 and the secondary light is improved. Thus, it is preferred thatintegral sintering is used to form the wavelength conversion member 14.As examples of specific materials for the wavelength conversion layer 14d and the heat transport layer 14 e, which are sintered integrally, whenYAG is used for the wavelength conversion layer 14 d, alumina may becombined as the heat transport layer 14 e.

In the modification of the embodiment, the wavelength conversion region14 a has the layered structure of the wavelength conversion layers 14 dand the heat transport layers 14 e, and the heat transport layers 14 eare able to favorably transport heat generated in the wavelengthconversion layers 14 d due to wavelength conversion to the holdingregion 14 b. As a result, heat dissipation is improved, making itpossible to prevent deterioration of wavelength conversion efficiencycaused by an excessive temperature increase in the wavelength conversionlayers 14 d.

Next the second embodiment of the disclosure is explained with referenceto FIG. 6. Explanation of parts duplicated with the first embodiment isomitted. FIG. 6 is a schematic sectional view of a lighting fixture unit20 in the second embodiment. This embodiment is a lighting fixture unitfor a vehicle, which is configured by using the light emitting device 10described in the first embodiment as a light source.

The lighting fixture unit 20 shown in FIG. 6 is configured so as to forma light distribution pattern for high beam. The lighting fixture unit 20is provided with the light emitting device 10, a cover 21, a lamp body22, a projection lens 23, a reflector 24 having an elliptic reflectingsurface that reflects emitted light towards the projection lens 23, aheat dissipation fin 25 that dissipates heat generated in the lightemitting device 10 outside through a base part 26, the base part 26 onwhich the light emitting device 10 is mounted, a swivel actuator 27, ascrew 29, a leveling actuator 30, and a screw 31.

The base part 26 is supported by the swivel actuator 27 so as to be ableto swivel in a horizontal direction. An upper part of the base part 26is connected with the lamp body 22 through the screw 31 and so on. Theswivel actuator 27 is connected with the leveling actuator 30. Theleveling actuator 30 moves a connecting member 28 by rotating the screw29, and is able to change inclination of the base part 26 in anupper-lower direction. Thus, the leveling actuator 30 is used forchanging an optical axis of the lighting fixture unit 20 and a lightdistribution pattern formed by the lighting fixture unit 20 in theupper-lower direction.

As shown in FIG. 1, wavelength of the primary light L1 emitted from thesemiconductor laser 12 is converted by the wavelength conversion member14 into the secondary light, and the white light L2 made by colormixture of the primary light L1 and the secondary light is emitted fromthe light emitting device 10. As shown in FIG. 6, the white lightemitted from the light emitting device 10 upwardly is reflected by thereflector 24 to the front, transmitted through the projection lens 23and the cover 21, and projected in front of the vehicle.

In the lighting fixture unit 20 in this embodiment, as shown in FIG. 4and FIG. 6, heat generated in the wavelength conversion region 14 a goesthrough the case part 13 and the stem 11 through the holding region 14b, is transferred to the heat dissipation fin 25 from the base part 26,and then dissipated. Therefore, in the lighting fixture unit 20 in theembodiment, it is also possible to realize stable white lightirradiation while favorably dissipating heat generated in the wavelengthconversion region 14 a.

Next, the third embodiment of the disclosure is explained with referenceto FIG. 7. Explanation of parts duplicated with the first embodiment isomitted. FIG. 7 is a schematic sectional view of a light emitting device40 in the third embodiment. The light emitting device 40 is providedwith a stem 41, a semiconductor laser 42, and a wavelength conversionmember 44. In the light emitting device 40, primary light L1 is emittedfrom the semiconductor laser 42 and irradiates the wavelength conversionmember 44. Then, a color of the primary light L1 is mixed with that ofsecondary light, which is obtained after wavelength conversion in thewavelength conversion member 44. Thus, the light emitting device 40emits white light outside.

In this embodiment, the wavelength conversion member 44 is a sinteredcompact in which a wavelength conversion region 44 a and a holdingregion 44 b are in contact with one another and formed integrally. Inthe wavelength conversion member 44 in this embodiment, the holdingregion 44 b is in contact with side surfaces and a bottom surface of thewavelength conversion region 44 a, forming a shape in which thewavelength conversion region 44 a is buried in the holding region 44 b.Further, the holding region 44 b has a structure in which a plurality ofceramic materials are intertwined with each other three-dimensionally.By making the refractive index difference between the ceramic materials0.2 or larger, the holding region 14 b becomes a white region as awhole, and also works as a light reflecting part.

The semiconductor laser 42 is arranged on an exposed surface side of thewavelength conversion region 44 a, and emits the primary light L1towards the wavelength conversion region 44 a. The primary light L1incident on the wavelength conversion region 44 a is extracted outsidefrom the exposed surface after the wavelength is converted by a phosphormaterial. As shown by an outlined arrow in FIG. 7, light advancing fromthe wavelength conversion region 44 a to the holding region 44 b isreflected by the holding region 44 b that serves as the light reflectingpart, caused to return towards the wavelength conversion region 44 a,and extracted outside.

As shown by a black arrow in FIG. 7, since the holding region 44 b hashigher thermal conductivity than that of the wavelength conversionregion 44 a, heat is favorably transferred and dissipated through theholding region 44 b and the stem 41. The holding region 44 b is obtainedby being in contact with the side surfaces and the bottom surface of thewavelength conversion region 44 a and sintered simultaneously.

Next, the fourth embodiment of the disclosure is explained withreference to FIG. 8. Explanation of parts duplicated with the firstembodiment is omitted. FIG. 8 is a schematic sectional view of a lightemitting device 50 in the fourth embodiment. The light emitting device50 is provided with a stem 51, semiconductor lasers 52, and a wavelengthconversion member 54. In the light emitting device 50, primary light L1from the semiconductor lasers 52 irradiates the wavelength conversionmember 54, and the color of the primary light L1 is mixed with that ofsecondary light, which is obtained after wavelength conversion at thewavelength conversion member 54. Thus, the light emitting device 50emits white light L2 outside.

In this embodiment, the wavelength conversion member 54 is also asintered compact in which a wavelength conversion region 54 a and aholding region 54 b are in contact with each other and formedintegrally. In the wavelength conversion member 54 in this embodiment,the holding region 54 b is in contact with side surfaces of thewavelength conversion region 54 a. Further, the holding region 54 b hasa structure in which a plurality of ceramic materials are intertwinedwith each other three-dimensionally. By making the refractive indexdifference among the ceramic materials 0.2 or larger, the holding region54 b becomes a white region as a whole, and also works as a lightreflecting part.

In this embodiment, the semiconductor lasers 52 are mounted on the stem51, the wavelength conversion member 54 is arranged on top of thesemiconductor lasers 52, and wavelength conversion region 54 a coverslight emitting positions of the semiconductor lasers 52. Wavelength ofthe primary light L1 incident on the wavelength conversion region 54 ais converted by the phosphor material, and the light is extractedoutside from an exposed surface. As shown by an outlined arrow in FIG.8, light directed from the wavelength conversion region 54 a towards theholding region 54 b is reflected by the holding region 54 b that servesas the light reflecting part, caused to return towards the wavelengthconversion region 54 a, and extracted outside.

As shown by black arrows in FIG. 8, since the holding region 54 b hashigher thermal conductivity than that of the wavelength conversionregion 54 a, heat is favorably transferred through the holding region 54b and dissipated. The holding region 54 b is in contact with the sidesurfaces of the wavelength conversion region 54 a and sinteredintegrally.

Next, the fifth embodiment of the disclosure is explained with referenceto FIG. 9. Explanation of parts duplicated with the first embodiment isomitted. FIG. 9 is a schematic sectional view of a light emitting device60 in the fifth embodiment. The light emitting device 60 is providedwith a stem 61, a semiconductor laser 62, and a wavelength conversionmember 64. In the light emitting device 60, primary light L1 from thesemiconductor laser 62 irradiates the wavelength conversion member 64,and the color of the primary light L1 is mixed with that of secondarylight emitted after wavelength conversion at the wavelength conversionmember 64. Thus, light emitting device 60 emits white light L2 outside.

In this embodiment, the wavelength conversion member 64 is also asintered compact in which a wavelength conversion region 64 a and aholding region 64 b are in contact with one another and formedintegrally. In the wavelength conversion member 64 in this embodiment,the holding region 64 b is in contact with a bottom surface of thewavelength conversion region 64 a, and the wavelength conversion region64 a is mounted on an upper surface of the holding region 64 b. Further,the holding region 64 b has a structure in which a plurality of ceramicmaterials are intertwined with each other three-dimensionally. By makingthe refractive index difference among the ceramic materials 0.2 orlarger, the holding region 64 b becomes a white region as a whole, andalso serves as a light reflecting part.

The semiconductor laser 62 is arranged on an exposed surface side of thewavelength conversion region 64 a, and emits the primary light L1towards the wavelength conversion region 64 a. The primary light L1incident on the wavelength conversion region 64 a is extracted outsidefrom the exposed surface after going through wavelength conversionperformed by a phosphor material. As shown by an outlined arrow in FIG.9, light directed from the wavelength conversion region 64 a to theholding region 64 b is reflected by the holding region 64 b that servesas the light reflecting part, caused to return towards the wavelengthconversion region 64 a, and extracted outside.

As shown by black arrows in FIG. 9, since the holding region 64 b hashigher thermal conductivity than that of the wavelength conversionregion 64 a, heat is favorably transferred and dissipated through theholding region 64 b and the stem 61. The holding region 64 b is incontact with the bottom surface of the wavelength conversion region 64 aand sintered simultaneously.

Next, the sixth embodiment of the disclosure is explained with referenceto FIG. 10A and FIG. 10B. Explanation of parts duplicated with the firstembodiment is omitted. FIG. 10A and FIG. 10B are schematic sectionalviews of configuration examples of a wavelength conversion member in thesixth embodiment. The wavelength conversion member, which is a sinteredcompact according to the disclosure, only needs to have a wavelengthconversion region 14 a and a holding region 14 b that are in contactwith each other and sintered integrally. The shapes of the wavelengthconversion region 14 a and the holding region 14 b are not limited tothose described in the first to fifth embodiments.

For example, as shown in FIG. 10A, the wavelength conversion region 14 ahaving generally cylindrical shape may be provided near the center ofthe flat plate-shaped holding region 14 b, and, as shown in FIG. 10B, atruncated cone-shaped wavelength conversion region 14 a may be provided.

In this embodiment, the wavelength conversion member 14 has thewavelength conversion region 14 a, which contains a phosphor materialthat performs wavelength conversion of primary light and emits secondarylight, and the holding region 14 b that is provided to be in contactwith the wavelength conversion region 14 a, and the wavelengthconversion member 14 is also a sintered compact in which the wavelengthconversion region 14 a and the holding region 14 b are sinteredsimultaneously and integrally, and is able to dissipate heat generatedwith the wavelength conversion efficiently.

Next, the seventh embodiment of the disclosure is explained withreference to FIG. 11. Explanation of parts duplicated with the firstembodiment is omitted. FIG. 11 is a schematic sectional view of a lightemitting device 70 in the seventh embodiment.

The light emitting device 70 is provided with a semiconductor laser 72,a wavelength conversion member 74, and a holder member 76. In the lightemitting device 70, primary light L1 from the semiconductor laser 72irradiates the wavelength conversion member 74, and the color of theprimary light L1 is mixed with that of secondary light emitted afterwavelength conversion at the wavelength conversion member 74. Thus, thelight emitting device 70 emits white light L2 outside.

As shown in FIG. 11, the wavelength conversion member 74 in thisembodiment is a sintered compact in which a wavelength conversion region74 a has a generally truncated cone shape, and a side surface of thewavelength conversion region 74 a is in contact with a holding region 74b and formed integrally. Also, a bottom surface of the wavelengthconversion region 74 a, which has the larger diameter, is an incidentsurface for the primary light L1, and the wavelength conversion region74 a is held so as to be tapered along an advancing direction of theprimary light L1. Since the side of the wavelength conversion region 74a with the smaller diameter serves as a light emitting surface, it ispossible to reduce a white light emitting area. In the shape shown here,the diameter of the wavelength conversion region 74 a is reducedgradually. However, the diameter may change in steps.

The holder member 76 is a plate-shaped member in which an opening isformed, and arranged on the light incident surface side of thewavelength conversion member 74 so that the wavelength conversion region74 a is exposed on the opening. The opening of the holder member 76 isformed so that its radius is smaller than that of the light incidentsurface of the wavelength conversion region 74 a by Δt, and arranged soas to become concentric with the wavelength conversion region 74 a. Amaterial for the holder member 76 is not limited as long as the holdermember 76 has rigidity to be able to hold the wavelength conversionmember 74. However, use of a ceramic material and metal having highthermal conductivity is preferred in order to improve heat dissipation.

Desired optical characteristics may be added to the opening of theholder member 76 by forming an optical film (not shown). For example,when a reflection film that transmits the primary light and reflects thesecondary light is formed, it is possible to prevent the secondary lightfrom being extracted from the incident surface side of the wavelengthconversion region 74 a. Thus, it becomes possible to extract white lightfrom the emitting surface side efficiently and restrain a decrease inluminous flux and brightness.

In this embodiment, concentration of a phosphor material contained inthe wavelength conversion region 74 a is low, and the thickness ofwavelength conversion region 74 a is increased compared to those in therelated art. For example, in the related art, a phosphor concentrationis in a range of 0.05˜0.5 atm %, and the thickness is about 0.1˜0.3 mm.However, in this embodiment, the phosphor concentration is within arange of 0.0005˜0.05 atm % and the thickness is about 1˜5 mm.

Since the concentration of the phosphor contained in the wavelengthconversion region 74 a is low, positions where heat is generated due towavelength conversion from the primary light to the secondary light aredispersed. Because the thickness of the wavelength conversion region 74a is large, an area in contact with the holding region 74 b becomeslarge. Due to the dispersion of heat generation positions and anincrease in the contact area, heat dissipation efficiency from thewavelength conversion region 74 a is improved. Further, by increasingthe diameter of the light incident surface side of the wavelengthconversion region 74 a, it is possible to improve wavelength conversionand heat dissipation simultaneously on the incident surface side wherelight intensity of the primary light is high. In this case, the primarylight advances in the wavelength conversion region 74 a and wavelengthconversion of the primary light is performed in the phosphor. Therefore,even if the diameter on the emitting surface side is reduced, wavelengthconversion of the primary light is performed efficiently. Also, byreducing the diameter of the emitting surface, brightness is improved.

In this embodiment, the side of the wavelength conversion region 74 awith the larger diameter serves as the incident surface, but the sidewith the smaller diameter may be the incident surface. In this case, thediameter expands along an advancing direction of the primary light, and,on the side surface of the wavelength conversion region 74 a in contactwith the holding region 74 b, light is reflected towards the emittingsurface having the larger diameter, and white light is extractedefficiently.

In this embodiment, the wavelength conversion member 74 also has thewavelength conversion region 74 a, which contains the phosphor materialthat performs wavelength conversion of the primary light and emits thesecondary light, and the holding region 74 b, which is provided to be incontact with the wavelength conversion region 74 a, and is a sinteredcompact in which the wavelength conversion region 74 a and the holdingregion 74 b are sintered simultaneously and integrally. Thus, thewavelength conversion member 74 is able to efficiently dissipate heatgenerated with wavelength conversion.

Next, a modification of the seventh embodiment is explained. As awavelength conversion member 74, instead of a sintered compact in whicha wavelength conversion region 74 a and a holding region 74 b are incontact with each other and formed integrally, a structure may beemployed in which the wavelength conversion region 74 a and the holdingregion 74 b are sintered separately and then combined with each other,and the holder member 76 prevents the wavelength conversion region 74 afrom falling.

In the modification of the embodiment, since the wavelength conversionregion 74 a and the holding region 74 b are formed as separate bodiesand combined together, freedom in the shapes of the wavelengthconversion region 74 a and the holding region 74 b is improved. Becausea holder member 76, which has an opening smaller than the wavelengthconversion region 74 a, is arranged on the side of the wavelengthconversion region 74 a with the larger diameter, it is possible toprevent the wavelength conversion region 74 a from falling from theholding region 74 b.

The disclosure is not limited to the foregoing embodiments, and variouschanges may be made within the scope of claims. The technical scope ofthe disclosure also includes embodiments that are obtained byappropriately combining technical means disclosed in the respectiveembodiments.

What is claimed is:
 1. A sintered compact comprising: a wavelengthconversion region containing a phosphor material that performswavelength conversion of primary light and emits secondary light; and aholding region provided to be in contact with the wavelength conversionregion, wherein the wavelength conversion region and the holding regionare integrated.
 2. The sintered compact according to claim 1, whereinthe holding region has higher thermal conductivity than that of thewavelength conversion region.
 3. The sintered compact according to claim1, wherein the holding region has a structure in which a minute secondceramic material is dispersed inside a first ceramic material and thefirst ceramic material and the second ceramic material are intertwinedwith each other three-dimensionally.
 4. The sintered compact accordingto claim 3, wherein the first ceramic material has higher thermalconductivity than that of the wavelength conversion region.
 5. Thesintered compact according to claim 3, wherein a refractive indexdifference between the first ceramic material and the second ceramicmaterial is 0.2 or larger.
 6. A light emitting device comprising: thesintered compact according to claim 1; and a light emitting element thatemits the primary light.